Today, pacemaker configuration is often performed by selecting a desired lead location for a specific patient (e.g., septal vs apical) and then programming the parameters of the pacemaker, such as the atrioventricular (AV) and/or interventricular (VV) delay, the rate responsive AV and/or VV delay and the like. Today, cardiac resynchronization therapy (CRT) configuration is similarly performed by selecting a desired lead location (e.g., by avoiding infarct zones, reduced dyssynchrony, left ventricle (LV) apical vs septal) and then programming the CRT device with desired AV and VV delays. The AV and VV delays are selected traditionally by physicians through the use of an echocardiography evaluation method. However, the echocardiography evaluation method is time consuming and has high variations.
In addition, device manufacturers have implemented algorithms within implanted medical devices that select AV and VV delays based on intra-cardiac electrograms (IEGM). For example, one device-based method uses P-wave duration to estimate intra-atrial conduction time for setting the timing of ventricular (V) pacing. This device-based method is intended to achieve similar effects as an echocardiography evaluation based method, namely to improve atrial-filling behavior. However, device-based methods that utilize the P-wave, as detected in the right atrium (RA), represent a rough estimation of intra-atrial conduction (IACT). As such, the potential exists that the P-wave estimate may be an inaccurate estimate of IACT.
Thus, these conventional selection methods currently utilize timing features (conduction delay, dyssynchrony measures), systemic hemodynamic measures (stroke volume, pre-load) and echocardiography evaluation bases measures of cardiac function for determining ejection time, myocardial performance index, left ventricular end systole volume, and left ventricular end diastole volume.
However, it is preferred to tailor each device to the individual patient's underlying etiology and functional status. Yet, a comprehensive echocardiography evaluation assessment is time consuming. Also, when the parameters of a pacemaker are set to a preferred setting, while a patient is in the clinic, the same parameter settings may not reflect the best parameter settings for the patient when the person is ambulatory and active.
A need remains for improved methods and systems for identifying and facilitating cardiac functions such as mechanical functions of select chambers.